Star A216 pH/RDO/DO BT Meter pH Range -2 to 20 Waterproof IP57 Automatic Temperature Compensation Yes Displayed Temperature Range 0 Degrees to 120 Degrees Operating Temp Range (F) 0 Degrees to 120 Degrees F Display High Resolution Mono-chromatic Auto Power Off Yes Calibration 5 point Cable Length 1 m Power Source AC or (4) AA Battery